Radio-frequency identification (RFID) tags are commonly used to store information that can be wirelessly interrogated. Information may be stored in a non-volatile memory contained in the tag. To reduce size and costs, passive RFID tags do not contain batteries; power is instead provided by an external field. For some operations, such as erasing and programing of the memory, a high-voltage is required. The high-voltage can be achieved with a charge pump, but the voltage level must be controlled to prevent damage to the tag and to ensure that the voltage is tuned for optimal memory performance. The voltage may be controlled using a reference voltage. A reference voltage should ideally provide a voltage that is constant across all operating temperatures of the tag.
Conventional techniques for producing a reference voltage, such as a bandgap reference voltage, typically require large currents (˜1 μA) and/or take up a large physical area (˜10000 μm2). For a passive RFID tag, however, the available current and physical area is limited. Conventional reference voltages can therefore consume a high proportion of the available space and current of such RFID tags.